Ms. Suarez said she received an email on Dec. 19 saying the item was en route. Since then, she said she has been on hold with customer service "forever."

She waited as long as possible, hoping for a last-minute Christmas miracle, but on Tuesday, with the clock ticking, she headed to Best Buy to purchase another Kindle Fire.

"Which really sucks to have to go to the store and stand in lines," she said Thursday.

Ms. Suarez works with homeless families in the city, and because of unpredictable work schedules, said she appreciates the convenience of shopping online.

"I understand (the meaning of) guaranteed," she said. "I trusted the company and I've shipped through UPS before. It's the holidays though, and you can't say you're going to ship an item and not ship. It's terrible because not everyone can afford to buy a replacement item. Now I have to ship it back when it comes -—it's a mess."

UPS and FedEx experienced shipping problems before Christmas, and delays were blamed on poor weather earlier this week in parts of the country and overloaded systems. The holiday shopping period this year was shorter than usual, more buying was done online and Americans' tendency to wait until the last second to shop probably didn't help either.

Neither company said how many packages were delayed, but noted it was a small share of overall holiday shipments. While the bulk of consumers' holiday spending remains at brick-and-mortar stores, shopping online is increasingly popular and outstripping spending growth in stores at the mall.

"UPS experienced heavy holiday volume and is making every effort to get packages to their destination as quickly as possible," the company said in a tweet Thursday. UPS did not make pickups or deliveries Wednesday.

UPS resumed normally scheduled service Thursday.

"We apologize that our customers did not receive their packages on Christmas," said Natalie Godwin, a spokeswoman for United Parcel Service Inc.

Some FedEx customers were able to pick up packages Christmas Day at their local FedEx Express centers.

"We're sorry that there could be delays and we're contacting affected customers who have shipments available for pickup," said Scott Fiedler, a spokesman for FedEx Corp.

Some readers who posted comments on the Telegram & Gazette Facebook page defended the delivery drivers.

"If you know somebody who works for UPS this time of the year you will know they are working from 8 am til 8 pm and beyond," the poster said. "UPS and FedEx are delivery companies not God. they cannot control the weather."

Others were critical of shoppers who wait until the last minute to place delivery orders.

"Christmas comes the same time every year... anyone who is upset about gifts not being on time have only one person to blame... themselves," the unsympathetic poster wrote.

UPS and FedEx customers were, however, not without their defenders, some of whom praised the companies for giving their employees the day off, but criticized the corporations for making promises they were unable to keep.

"Christmas isn't a new concept maybe the companies should make adjustments for when they know they will be busy... I know when I'm busy at work I have to step it up to make sure everyone's happy no excuses and I don't get extra help. It's my job and it's what I have to do. Bottom line," one writer noted.

Lisa Shumski of Marlboro ordered a gift for her youngest granddaughter from Target, and had expected FedEx to deliver it in time for Christmas. The package was picked up on Dec. 19 in Carson, Calif., and made it as far as Bloomington, Calif., the next day. FedEx has not sent her any further updates, but tracking information indicated the package was to be delivered Thursday.

Ms. Shumski said early Thursday that she did not see how that would be possible because the package appeared to still be in California. However, when she checked back Thursday evening, she learned it was actually in Wilmington, Conn., and scheduled to reach her doorstep today.

Heavy spending in the final days of the mostly lackluster season sent sales up 3.5 percent between Nov. 1 and Tuesday, according to MasterCard Advisors SpendingPulse, which tracks payments but doesn't give dollar figures.

Online shopping led the uptick, with spending up 10 percent to $38.91 billion between Nov. 2 and Sunday, research firm comScore said.

''We always have last-minute Charlies, but this year even people who normally complete shopping earlier completed shopping later,'' said Marshal Cohen, chief retail analyst at market research firm NPD Group.

Justin Londagin and his wife ordered their 7-year-old son a jersey featuring Russell Wilson of the Seattle Seahawks from NFL's website on Dec. 19. They paid $12.95 extra for two-day shipping to get it to their Augusta, Kan., home before Christmas, but it didn't arrive in time. ''We had to get creative and wrote him a note from Santa to tell him that the jersey fell out of the sleigh and Santa will get it to him as soon as he could,'' he said.

Amazon is offering customers with delayed shipments a refund on their shipping charges and $20 toward a future purchase. And other retailers such as Macy's said they are looking into the situation.

The last-minute surge this year solidifies the increasing popularity of online shopping, which accounts for about 10 percent of sales during the last three months of the year. It also underscores the challenges that companies face delivering on the experience, particularly during the holiday shopping season that runs from the beginning of November through December.

Analysts say FedEx and UPS typically work closely with big retailers to get a sense of the volume of packages they'll handle during peak times like the holiday season. Extra flights, trucks and seasonal workers can be added if the projections are large.

But this year, David Vernon, a senior research analyst at Sanford C. Bernstein, said weather played a role. The early December ice storms in Dallas could have hurt operations, he said, and packages can start to accumulate. And that got compounded by a late surge in shipments, he said.

''Clearly, as a group, (they) underestimated the demand for Internet retailing during the holidays,'' Vernon said.

Another problem was the growing popularity of retailers offering free shipping. Amazon, for one, has a two-day free shipping offer that comes with its $79 annual Prime membership. The company said in the third week of December alone, more than 1 million people signed up for the membership.

''Frankly the right hand wasn't talking to the left,'' said Forrester analyst Sucharita Mulpuru. ''The marketing teams of a lot of Web retailers (offering free shipping) were not talking to the operations and supply chain teams.''

''The central pillar of their business is a perception of reliability with their customers,'' said Jeremy Robinson-Leon, CEO of Group Gordon, a corporate and crisis PR firm. This year's snafus ''just really erodes trust among customers.''

The resulting delayed shipments could be a problem for shippers. UPS and FedEx did not quantify how many packages were affected.

The Associated Press contributed to this story. Contact Linda Bock via email at lbock@telegram.com. Follow her on Twitter @LindaBockTG